In Chapter 27 of The Grapes of Wrath, work is found by the migrant workers picking cotton, something they had done on their own farms. However, while there is money enough to eat, more people are arriving than there are jobs available.

As Chapter 28 begins, readers find that the Joads are able to occupy half of a train car instead of living in a tent. When Ma buys a treat for Ruthie and Winfield, a fight breaks out between Ruthie and another girl, and so she reveals that Tom has killed two people with the intention of frightening the other girl.

Tom has been hiding out and Ma finds him to tell him he must leave. Tom has been introspective and decides that he will take up where Casy left off, helping the world at large: to do this, he feels he must unite the people, and will go wherever he is needed.

The Wainwrights are fearful that Al is going to disgrace the family by getting Aggie pregnant; Ma offers to speak to Al. Meanwhile, Pa is growing depressed, believing that their future is very bleak. Ma remains strong, refusing to give up.

Al and Aggie announce their engagement. The families celebrate, and the next day go into the fields early to pick cotton, but by the time they arrive, little is left to collect. Returning "home," they find that Rose of Sharon is not well.

Chapter 29 sees miserable weather settling in. Continued rain washes out cars and tents. Water covers the land and flooding causes people to look for higher ground. Food becomes scares again, and argue ensues.

At the start of Chapter 30, Al covers the car's engine to keep it dry. Now the two families, the Joads and the Wainwrights, have joined forces, drawn together by their engaged children. Pa leads other men to build an embankment to stem the flow of the water. Returning he discovers Sharon's baby has died in childbirth.

When Ma speaks with Mrs. Wainwright, she once again echoes how the Depression has contributed to the disintegration of her family. Later the family separates forage for alternative living conditions, and Ma and the others find a barn that looks dry. Inside they find a boy sitting with his starving father, saying that the sick man needs milk. Rose of Sharon offers the baby's milk she cannot use to the man, as her child is dead, thereby offering the gift of survival to a stranger—in fact, she is helping a member of the larger community of which all the migrant workers are a part.